Selectively coupling one of two interfaces in an external memory apparatus to a personal computer depending upon a configuration of the computer and a single bus interface

ABSTRACT

A CD-ROM apparatus is provided with an IDE-BUS interface and an ISA-BUS interface and a switching circuit for switching there between. In another embodiment invention is provided to simplify building a personal computer having a CD-ROM apparatus as an external memory and using an IDE-BUS I/F for connecting to the CD-ROM apparatus. Thus a hard disk unit is connected to a master partition of the IDE-BUS I/F of the personal computer, and the CD-ROM apparatus is connected to a slave partition of the IDE-BUS interface.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/545,488, filed Apr. 10, 2000, now U.S. Pat. No. 6,539,442; which is acontinuation-in-part of U.S. patent application Ser. No. 08/985,584,filed Dec. 5, 1997, now abandoned; which is a continuation of U.S.patent application Ser. No. 08/276,440, filed Jul. 18, 1994, nowabandoned; which claims priority under 35 U.S.C. §119 to Japanese PatentApplication No. 5-041032, filed Jul. 28, 1993, and all beingincorporated by reference herein for all purposes.

BACKGROUND OF THE INVENTION

This invention relates to a CD-ROM (compact disk read only memory)apparatus and, more particularly, to a CD-ROM apparatus used as anexternal memory of a personal computer.

DESCRIPTION OF THE RELATED TECHNOLOGY

A general connection example of a conventional CD-ROM apparatus of thistype for a personal computer system will be described by referring toFIG. 2 (Prior Art). Numeral 1 denotes a body of a personal computer, andnumeral 2 designates a CPU. A ROM 3 and a RAM 4 of an internal memoryare connected to the CPU 2. The CPU 2 is connected to an AT-BUS 6through a BUS controller 5, and further connected to devices through theAT-BUS 6.

On the other hand, with respect to an external memory, an IDE-BUS I/F(interface) 7 is connected to the AT-BUS 6, and hard disk devices 8 areconnected to the IDE-BUS I/F 7 through an IDE-BUS 9. In this case, thehard disk devices 8 can be connected to the IDE-BUS I/F 7 according tothe IDE standards. An ISA-BUS I/F 10 is connected to the AT-BUS 6. AnI/F CARD connector 12 is connected to the ISA-BUS I/F 10 through anISA-BUS 11, and a CD-ROM apparatus 13 containing an I/F 13 acorresponding in operation to the ISA-BUS standard is connected to theIF/CARD connector 12 through an I/F CABLE 14.

The conventional CD-ROM apparatus of the personal computer, as describedabove, is corrected to the ISA-BUS I/F 10 through the I/F CARD connector12. That is, when the CD-ROM apparatus 13 is used as an external memory,the I/F CARD connector 12 and the I/F CABLE 14 are required in additionto the CD-ROM apparatus 13. When the user connects the CD-ROM apparatus13 to the personal computer 1, it is necessary to supply and set the I/FCARD connector 12 into the computer 1.

Therefore, eliminating the I/F CABLE 14 and the I/F CARD connector 12would make for a simpler connection of the CR-ROM apparatus 13 to thecomputer 1.

Accordingly, it is an object of this invention to provide a CD-ROMapparatus which can simplify and reduce expenses in construction of apersonal computer system.

SUMMARY OF THE INVENTION

The present invention achieves the above-described object, by providinga CD-ROM apparatus comprising an IDE interface, wherein a hard disk unitand the CD-ROM apparatus are connected in cascade with the IDE interface(IDE I/F) of a personal computer.

The IDE I/F of the personal computer is partitioned for both master andslave devices. The hard disk unit is ordinarily connected to the masterpartition. Further, the CD-ROM apparatus is ordinarily connected to theslave partition of the IDE I/F of the personal computer. Thus, theCD-ROM apparatus is connected in cascade with the hard disk unit on anIDE-BUS connected to the IDE I/F. However, according to an embodiment ofthe present invention, the CD-ROM apparatus may be connected to themaster partition and the hard disk connected to the slave partition ofthe IDE I/F by changing the logic state of a drive selection bit in theIDE bus interface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a computer system according to anembodiment of this invention;

FIG. 1A is a schematic block diagram of a computer system according toanother embodiment of this invention; and

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of the present invention will be described in detail withreference to FIG. 1. In FIG. 1, the same reference numerals as thoseused in prior art of FIG. 2 designate corresponding elements, and adetailed description thereof will be omitted. In FIG. 1, referencenumeral 15 denotes a CD-ROM apparatus. An IDE-BUS I/F 15 a is added inthe CD-ROM apparatus 15. A hard disk unit 8 may be connected as either amaster or slave of the IDE-BUS I/F 7 of a personal computer indicated bythe numeral 1, and the CD-ROM apparatus 15 may be connected as either aslave or master of the IDE-BUS I/F 7. The IDE-BUS I/F 7 uses 1-bit of aregister 18 as a drive selection bit, and determination of which deviceis to be the master or the slave is selected by switching or togglingthis drive selection bit of the register 18 by a CD-ROM driver program.

Thus, the I/F CARD connector 12 and the I/F CABLE 14 described withrespect to the prior art of FIG. 2 are eliminated from the configurationof this invention which reduces its cost due to deletion of a number ofthe components and eliminates the work of building the I/F CARDconnector 12 into the personal computer 1.

Further, since the CD-ROM driver is moved independently from a BIOS of asystem program in a software, it is not necessary to alter the BIOS andother basic program.

Then, the CD-ROM apparatus 15 is selectably connected to the slave ormaster partition of the IDE-BUS I/F 7 of the personal computer 1, andthe hard disk unit 8 is selectably connected to the master or slavepartition, respectively, of the IDE-BUS I/F 7, according to the logicstate of the drive selection bit of the register 18. The logic state ofthe drive selection bit of the register 18 is controlled by the computersoftware process (i.e., CD-ROM driver program).

An IDE-BUS I/F 15 a and an ISA-BUS I/F 15 b are provided in the CD-ROMapparatus 15, and further switching circuit 15 c is added to use both byswitching the switching circuit 15 c even if the configuration of thepersonal computer is different.

The present invention may be variously modified within the scope of thespirit of the present invention, and the modifications thereof will benaturally included in the scope of the present invention.

This invention provides, as described above, the CD-ROM apparatus 15comprising an IDE BUS interface 15 a, wherein a hard disk unit 8 and theCD-ROM apparatus 15 are connected in cascade with the IDE interface 7 ofthe personal computer 1. Therefore the I/F CARD connector 12 and the I/FCABLE 14 (FIG. 2) which were heretofore required to connect the CD-ROMapparatus 13 to the ISA-BUS I/F 10 of the personal computer 1, can beeliminated.

As described above, expenses required for the I/F CARD connector 12 andthe I/F CABLE 14 are eliminated along with the cost of labor forbuilding the I/F CARD connector 12 into the computer system 1.

The invention, therefore, is well adapted to carry out the objects andattain the ends and advantages mentioned, as well as others inherenttherein. While the invention has been depicted, described, and isdefined by reference to particular preferred embodiments of theinvention, such references do not imply a limitation on the invention,and no such limitation is to be inferred. The invention is capable ofconsiderable modification, alteration, and equivalents in form andfunction, as will occur to those ordinarily skilled in the pertinentarts. The depicted and described preferred embodiments of the inventionare exemplary only, and are not exhaustive of the scope of theinvention. Consequently, the invention is intended to be limited only bythe spirit and scope of the appended claims, giving full cognizance toequivalents in all respects.

What is claimed is:
 1. An external memory apparatus for use with apersonal computer comprising: an IDE-BUS interface formed within theexternal memory apparatus; a second interface formed within the externalmemory apparatus; a switching circuit coupled to said IDE-BUS interfaceand said second interface; and a single BUS interface only coupledbetween the external memory apparatus and the personal computer, wherebysaid IDE-BUS interface and said second interface may be selectively usedby switching said switching circuit depending upon a configuration ofthe personal computer and the single BUS interface.
 2. An externalmemory apparatus for use with a personal computer as in claim 1 wherein:the external memory apparatus reproduces a function of a CD-ROMapparatus.
 3. An external memory apparatus for use with a personalcomputer as in claim 1 wherein: the external memory apparatus comprisesa CD-ROM apparatus.
 4. An external memory apparatus for use with apersonal computer as in claim 1 wherein: said second interface comprisesa ISA-BUS interface.
 5. A personal computer system comprising: apersonal computer having a first and second computer BUS interface; anexternal memory apparatus coupled to said personal computer; a firstexternal memory apparatus BUS interface formed within said externalmemory apparatus; a second external memory apparatus BUS interfaceformed within said external memory apparatus; a switching circuit formedwithin said external memory apparatus and coupled to said first andsecond external memory apparatus BUS interface; and a single one only ofthe first and second computer BUS interfaces coupled between saidexternal memory apparatus and said personal computer system, wherebyeither of said first and second external memory apparatus BUS interfacesmay be selectively used by switching said switching circuit dependingupon a configuration of said personal computer and the single one onlyof the first and second computer BUS interfaces.
 6. A personal computersystem as in claim 5 wherein: said external memory apparatus comprises aCD-ROM apparatus.
 7. A personal computer system as in claim 5 wherein:said first external memory apparatus BUS interface comprises an IDE-BUSinterface; and said second external memory apparatus BUS interfacecomprises a ISA-BUS interface.
 8. An external memory apparatus for usewith a personal computer comprising: a first interface formed withinsaid external memory apparatus; a second interface formed within saidexternal memory apparatus; and a single BUS interface only coupledbetween the external memory apparatus and the personal computer, wherebyeither of said first and second interface may be selectively coupled tothe personal computer depending upon a configuration of the personalcomputer and the single BUS interface.
 9. An external memory apparatusfor use with a personal computer as in claim 8 wherein: the externalmemory apparatus comprises a function for reproducing CD-ROM apparatus.10. An external memory apparatus for use with a personal computer as inclaim 8 wherein: the external memory apparatus comprises CD-ROMapparatus.
 11. An external memory apparatus for use with a personalcomputer as in claim 8 wherein: said first interface comprises IDE-BUSinterface.
 12. An external memory apparatus for use with a personalcomputer as in claim 8 wherein: said second interface comprises ISA-BUSinterface.
 13. A personal computer system comprising: a personalcomputer having a first and second computer BUS interface; an externalmemory apparatus coupled to said personal computer; a first externalmemory apparatus BUS interface formed within said external memoryapparatus; a second external memory apparatus BUS interface formedwithin said external memory apparatus; and a single BUS interface onlycoupled between said external memory apparatus and said person computer,whereby either of said first and second interface may be selectivelycoupled to said personal computer depending upon a configuration of saidpersonal computer and the single BUS interface.
 14. A personal computersystem as in claim 13 wherein: said external memory apparatus comprisesa function for reproducing CD-ROM apparatus.
 15. A personal computersystem as in claim 13 wherein: said external memory apparatus comprisesCD-ROM apparatus.
 16. A personal computer system as in claim 13 wherein:said first interface comprises IDE-BUS interface.
 17. A personalcomputer system as in claim 13 wherein: said second interface comprisesISA-BUS interface.
 18. A CD-ROM external memory apparatus for use with apersonal computer comprising: an IDE-BUS interface provided in theCD-ROM external memory apparatus; an ISA-BUS interface provide in theCD-ROM external memory apparatus; a switching circuit coupled to saidIDE-BUS interface and said ISA-BUS interface; and a single BUS interfaceonly coupled between the CD-ROM external memory apparatus and the personcomputer, whereby said IDE-BUS interface and said ISA-BUS interface maybe selectively used by switching said switching circuit even if theconfiguration of the personal computer is different.